Fix merge objects

Author: nekohasekai

common/json/badjson/merge_objects.go

@@ -2,9 +2,11 @@ package badjson
 
 import (
 	"context"
+	"reflect"
 
 	E "github.com/sagernet/sing/common/exceptions"
 	"github.com/sagernet/sing/common/json"
+	cJSON "github.com/sagernet/sing/common/json/internal/contextjson"
 )
 
 func MarshallObjects(objects ...any) ([]byte, error) {
@@ -31,16 +33,12 @@ func UnmarshallExcluded(inputContent []byte, parentObject any, object any) error
 }
 
 func UnmarshallExcludedContext(ctx context.Context, inputContent []byte, parentObject any, object any) error {
-	parentContent, err := newJSONObject(ctx, parentObject)
-	if err != nil {
-		return err
-	}
 	var content JSONObject
-	err = content.UnmarshalJSONContext(ctx, inputContent)
+	err := content.UnmarshalJSONContext(ctx, inputContent)
 	if err != nil {
 		return err
 	}
-	for _, key := range parentContent.Keys() {
+	for _, key := range cJSON.ObjectKeys(reflect.TypeOf(parentObject)) {
 		content.Remove(key)
 	}
 	if object == nil {

common/json/internal/contextjson/keys.go

@@ -0,0 +1,20 @@
+package json
+
+import (
+	"reflect"
+
+	"github.com/sagernet/sing/common"
+)
+
+func ObjectKeys(object reflect.Type) []string {
+	switch object.Kind() {
+	case reflect.Pointer:
+		return ObjectKeys(object.Elem())
+	case reflect.Struct:
+	default:
+		panic("invalid non-struct input")
+	}
+	return common.Map(cachedTypeFields(object).list, func(field field) string {
+		return field.name
+	})
+}

common/json/internal/contextjson/keys_test.go

@@ -0,0 +1,26 @@
+package json_test
+
+import (
+	"reflect"
+	"testing"
+
+	json "github.com/sagernet/sing/common/json/internal/contextjson"
+
+	"github.com/stretchr/testify/require"
+)
+
+type MyObject struct {
+	Hello string `json:"hello,omitempty"`
+	MyWorld
+	MyWorld2 string `json:"-"`
+}
+
+type MyWorld struct {
+	World string `json:"world,omitempty"`
+}
+
+func TestObjectKeys(t *testing.T) {
+	t.Parallel()
+	keys := json.ObjectKeys(reflect.TypeOf(&MyObject{}))
+	require.Equal(t, []string{"hello", "world"}, keys)
+}